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Is planting trees the solution to reducing flood risks?

Lookup NU author(s): Dr Jayne Carrick, Cosmos Adjei, Hassan Ashraa Kalee, Steven Banks, Dr Rike Bolam, Ivone Campos Luna, Dr Beth ClarkORCiD, Dr Jake Cowton, Israel Domingos, David Golicha, Garima Gupta, Dr Matthew Grainger, Gultan Hasanaliyeva, David Hodgson, Dr Elisa Lopez-Capel, Dr Amelia Magistrali, Dr Ian Merrell, Dr Idiegberanoise Oikeh, Mwana Othman, Thilanka Ranathunga, Dr Carl Samuel, Enas Sufar, Philip Watson, Nik Zakaria, Dr Gavin Stewart



This is the authors' accepted manuscript of an article that has been published in its final definitive form by Wiley-Blackwell, 2019.

For re-use rights please refer to the publisher's terms and conditions.


© 2018 The Chartered Institution of Water and Environmental Management (CIWEM) and John Wiley & Sons Ltd Flood risk and associated impacts are major societal and policy concerns following widespread flooding in December 2015, which cost the UK economy an estimated £5 billion. Increasing advocacy for alternatives to conventional hard engineering solutions is accompanied by demands for evidence. This study provides a systematic review and meta-analysis of direct evidence for the effect of tree cover on channel discharge. The results highlighted a deficiency in direct evidence. From 7 eligible studies of 156 papers reviewed, the results show that increasing tree cover has a small statistically significant effect on reducing channel discharge. Meta-analysis reveals that tree cover reduces channel discharge (standardised mean difference −0.35, 95%CI, −0.71 to 0.00), but the effect was variable (I2 = 81.91%), the potential for confounding was high, and publication bias is strongly suspected (Egger Test z = 3.0568, p =.002). Due to the lack of direct evidence the overall strength of evidence is low, indicating high uncertainty. Further primary research is required to understand reasons for heterogeneity and reduce uncertainty. A Bayesian network parameterised with data from the meta-analysis supports investment in integrated catchment management, particularly on infrastructure density and water storage (reservoirs), for effective responses to flood risk.

Publication metadata

Author(s): Carrick J, Abdul Rahim MSAB, Adjei C, Ashraa Kalee HHH, Banks SJ, Bolam FC, Campos Luna IM, Clark B, Cowton J, Domingos IFN, Golicha DD, Gupta G, Grainger M, Hasanaliyeva G, Hodgson DJ, Lopez-Capel E, Magistrali AJ, Merrell IG, Oikeh I, Othman MS, Ranathunga Mudiyanselage TKR, Samuel CWC, Sufar EKH, Watson PA, Zakaria NNAB, Stewart G

Publication type: Article

Publication status: Published

Journal: Journal of Flood Risk Management

Year: 2019

Volume: 12

Issue: S2

Online publication date: 17/07/2018

Acceptance date: 02/07/2018

Date deposited: 23/09/2019

ISSN (electronic): 1753-318X

Publisher: Wiley-Blackwell


DOI: 10.1111/jfr3.12484


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